This invention generally relates to linear actuators and lift jacks and, more specifically, to a telescoping linear actuator.
Many industries require that large loads be lifted, moved, or repositioned. Often, the load must be moved a significant distance and then precisely positioned at a new location. Typically the load is moved using an actuator or lift jack. Unfortunately, there is a tradeoff in the amount of space that these systems occupy because when in a collapsed state typical non-telescoping actuators are longer than their stroke. When using the typical non-telescoping actuator, this may result in the actuator taking up more space around the work area than desired. In specific lift jack applications, this may result it being unusable because the lift jack cannot be inserted underneath the load.
Generally, these problems are solved by utilizing telescoping hydraulic rams. These rams and the systems within which they operate are still susceptible to failure, possibly leading to a falling load. Further, precise positioning with telescoping hydraulic rams is difficult unless delicate instruments (e.g., linear variable differential transformers) are placed along an exterior longitudinal axis of the ram to measure its longitudinal displacement. These delicate instruments are often subject to interference or damage when used in rough environments. Accordingly, a loss of confidence in the position of the load and significant safety issues may result from the use of telescoping hydraulic rams.
With respect to previous telescoping linear actuators, a known limitation is that an external force must be applied at the tip of the actuator, usually by a load being lifted, to prevent the stage nearest the tip from turning. If the stage nearest the tip of the actuator turns during deployment, rather than simply extending, the position of the load will not be known. Further, if the load is used to prevent rotation of the tip, significant forces may be introduced to the load that may not be allowable, thereby limiting the application of the actuator. Throughout this application the terms “stage” and “segment” are used interchangeably and should be understood to have the same meaning.
Accordingly, a better solution is needed that does not rely on a force applied by a load to prevent a stage from rotating and permits precise positioning of a load by an actuator that has a high volumetric efficiency.